According to the Internet, slurry ice is a phase changing refrigerant made up of millions of ice “micro-crystals” (generally 0.1 to 1 mm in diameter) formed and suspended within a solution of water and a freezing point depressant. Some compounds used in the field are salt (sodium chloride), ethylene glycol, propylene glycol, various alcohols (Isobutyl, ethanol) and sugar (sucrose, glucose). Slurry Ice has greater heat absorption compared with single phase refrigerants (Brine) because the melting enthalpy (latent heat) of the ice is also used. Flow-Ice™ is a trade name for slurry ice. Flow-Ice™ is made with a heat exchanger.
The small ice particle size of slurry ice results in greater heat transfer area than other types of ice for a given weight. It can be packed inside a container as dense as 700 kg/m3, the highest ice-packing factor among all usable industrial ice. The spherical crystals have good flow properties, making them easy to distribute through conventional pumps and piping and over product in direct contact chilling applications, allowing them to flow into crevices and provide greater surface contact and faster cooling than other traditional forms of ice.
Its flow properties, high cooling capacity and flexibility in application make a slurry ice system a substitute for conventional ice generators and refrigeration systems, and offers improvements in efficiency: energy efficiency of 70%, compared to around 45% in standard systems, lower freon consumption per ton of ice and lower operating costs.
Slurry ice is commonly used in a wide range of air conditioning, packaging, and industrial cooling processes, supermarkets, and cooling and storage of fish, produce, poultry and other perishable products.
Conventional current slurry ice producing technologies include the following:
(a) Orbital Rod Tube Whip Heat Exchanger
Orbital rod tube heat exchanger include a rod which rotates centrifugally in each tube of a vertical shell and tube heat exchanger, and a film of brine drains down the tube by gravity and carry the ice created down to exit the heat exchanger. The orbital rod induces the heat transfer. This technology has a drive plate to drive a multiple of rods hanging from the top and has the tendency to vibrate and does not suit needs in terms of robust operation. This technology is more suited for thermal energy storage where all fluids and conditions are designed for the operation.
(b) Flat Plate Heat Exchanger
The flat plate heat exchanger is more robust in operation, but will not cover the full scope of slurry ice needs, and the capacity is too small for larger applications. The flat plate heat exchanger is also very costly to manufacture and requires a refrigerant pump, pressure vessels and controls that further increase the cost, making the system too expensive. The general operation is wipers wiping both sides of a flat plate or multiples of flat plates mounted parallel with each other and the drive shaft of the wipers drives through the centre of the plates to wipe the static plates removing the crystals forming on the surface with refrigerant in the flat plate channels.
(c) Scraped Surface Heat Exchangers
This type of heat exchanger is too small and also too costly to upscale to larger systems. It is based on a larger diameter tube with thicker walls reducing the heat transfer rate. The scraping mechanism is very costly to manufacture and the system requires a carefully designed system to make it successful in operation. The basic operation is based on a double tube heat exchanger with the refrigerant circulated through the jacket and the brine though the inner tube. The ice crystals are formed on the inner tube surface and scraped of with a scrapers or wipers and transported out with a pump pushing the brine or slurry ice.
It is an object of the invention to suggest a industrial shell and tube heat exchanger, which will assist in overcoming these problems.